[PaulProe]

Bill,
Two stage is necessary to get to 150-175 psi. Unless you have an in-ground lift or a tire changer, there is little need for that high of pressure. Most air tools call for regulation to 90-100 psi which a single stage will do.

Smaller compressors (up to 5hp) generally are single stage since it gets more air with less horsepower.

Most industrial types over 5HP are two stage. Don't be fooled by HP. The government actually came down on the industry, making them recall a bunch of mis-labeled units. The most important factor is output (CFM) at a standard pressure (generally 100psi). Some use "90psi" so their output CFM appears higher. It really becomes a marketing game.

There are some cheap units out there - you get what you pay for. Anything less than $1,000 is definitely not industrial grade.

Paul